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    ex_4.2_atof_scientific@learntosolveit
    Open on Replit
    main
    main.c
    Makefile
    Config files
    .replit
    replit.nix
    #include <stdio.h>
    #include <ctype.h>

    #define MAXLINE 100

    double atof(char s[]);
    int mgetline(char s[], int lim);

    int main(int argc, char *argv[])
    {
    char str[MAXLINE];
    double val;

    mgetline(str, MAXLINE);

    val = atof(str);

    printf("%f", val);

    return 0;
    }

    double atof(char s[])
    {
    double val, pow;
    int sign, i, esign, exp;

    int power(int base, int exp);

    for (i = 0; isspace(s[i]); i++)
    ;

    sign = (s[i] == '-') ? -1 : 1;

    if (s[i] == '+' || s[i] == '-')
    i++;

    for (val = 0.0; isdigit(s[i]); i++)
    val = 10.0 * val + (s[i] - '0');

    if (s[i] == '.')
    i++;

    for (pow = 1.0; isdigit(s[i]); i++) {
    val = 10.0 * val + (s[i] - '0');
    pow *= 10.0;
    }

    if (s[i] == 'e' || s[i] == 'E')
    i++;

    if (s[i] == '+')
    esign = 1;
    else if (s[i] == '-')
    esign = -1;
    else
    esign = 1;

    for (exp = 0; isdigit(s[i]); i++)
    exp = 10 * exp + (s[i] - '0');

    if (esign == 1)
    val = (val / pow) * power(exp, 10);
    else
    val = (val / pow) / power(exp, 10);

    return sign * val;
    }

    int mgetline(char s[], int lim)
    {
    int c, i;

    for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i)
    s[i] = c;

    if (c == '\n') {
    s[i] = c;
    ++i;
    }

    s[i] = '\0';

    return i;
    }

    int power(int base, int exp)
    {
    int i, p;

    p = 1;

    for (i = 1; i <= exp; ++i)
    p = p * base;

    return p;
    }